— ST 
from the Lias and Oolites. 25 
areas, the closeness and smallness of their rows of tubercles, the 
granular band down the centre of the interambulacra, and the 
unequal size of its component tubercles, alike contribute to make 
the deception almost complete. 
The most remarkable parts of the structure of this tiny fossil 
are the spines, which in some crushed specimens are preserved 
in situ; they are long, delicate and hair-like, and have large 
articular heads; these spines look like so many bristles laid down 
in all directions upon some slabs of the Lias shales ; in a crushed 
test of four-tenths of an inch in diameter the spines measured an 
inch and a half in length. 
Affinities and differences.—The only Cidarites for which A. cri- 
nifera is likely to be mistaken are Diadema Moorei and Pedina 
Etheridgii ; from the former it is easily distinguished by the nar- 
rowness of the ambulacral areas and the smallness of the tubercles 
thereof ; from the latter it differs in the comparative smallness of 
its ambulacral areas, and above all in having the mammillary 
eminences of its tubercles deeply crenulated, a character which is 
absent in all the Pedinas we know; at present we know of no 
other Urchin in the Lias for which it can be mistaken. 
Locality and stratigraphical range.—A. crinifera has been 
found only in the lower shales of the lower Lias near Lans- 
downe, Cheltenham, and in the same stratum near Gloucester ; it 
is associated wtth Turrilites Valdani, D’Orbig., and Ammonites 
oxynotus, Quenstedt. It has been collected by Prof. Quenstedt 
in the lowest schist of the “ Posidonienschiefer von Pliensbach 
bei Boll” in Wiirtemberg. We have before us now two slabs 
of this curious bed ; one surface of the slab is covered over with 
the long hair-like spines strewed about in all directions, with 
here and there the crushed test of one of these Urchins with its 
spines attached and in sitw. 
History.—Described by Mr. Buckman under the name Echinus 
minutus, but previously noticed by M. Quenstedt in his work 
on the Fleetzgebirge of Wiirtemberg ; it has been recently figured 
by him in his ‘ Handbuch der Petrefactenkunde,’ under the name 
Cidarites criniferus. 
Diadema Davidsoni, Wright. PI. II. fig. 2, a-e. 
Test depressed, circular; tubercles elevated upon prominent 
mammillary eminences; pores in a single file throughout; a 
few small secondary tubercles in the interambulacra ; the pri- 
mary ambulacral tubercles nearly as large as those of the 
interambulacra. 
Height ,%ths of an inch, transverse diameter 1 inch and {6 ths. 
Description.—This beautiful Urchin has a regular circular 
